Hammer for hammer mills



Feb. 6, 1968 R. w. STEINBERG HAMMER FOR HAMMER MILLS Filed June 9, 1965 EQUIN- c m mfim mwwm a mi wLQWA 0Ww% w? R United States Patent M 3,367,584 HAMMER FOR HAMMER MILLS Richard W. Steinberg, Owatonna, Minn., assignor to Owatonna Manufacturing Company, Inc., Owatonna, Minn., a corporation of Minnesota Filed June 9, 1965, Ser. No. 462,698 7 Claims. (Cl. 241-195) ABSTRACT OF THE DISCLOSURE A hammer mill hammer having an outer generally rectangular head end portion defining sharp corner edges and a blade-like shank portion for mounting on a hammer mill rotor and having opposite side surfaces uniformly curved between the opposite side edges thereof to provide a cross sectionally streamline form.

Background of the invention This invention relates generally to improvements in hammer mills of the type commonly used in the prepararation of animal feed and the like, and more specifically to improvements in the construction of generally radial blades or hammers of such hammer mills.

It is generally known among those familiar with the art that conventional hammer mills not only require substantial power for efficient operation, but also generate an objectionable amount of noise during the operation thereof, both due to extreme turbulence which occurs within the machine. It is further recognized that, in hammer mills having radially disposed blades or hammers, substantially all of the grinding or comminuting of the material in the mill chamber is achieved by the radially outer end portions of the hammers, and that the radially inner portions of the blades or hammers are substantially free from engagement with the material being ground. Hammers heretofore produced have been stamped from sheet or plate metal, or have comprised enlarged radially outer heads clamped or bolted on cross sectionally reduced shanks for mounting on hammer mill rotors. Such shanks are cross sectionally rectangular or round, being relatively heavy and expensive to produce, and add substantially to the noise level of hammer mills and to the turbulence therein when rotating at high speeds.

Summary of the invention An important object of this invention is the provision of a hammer for hammer mills which requires less power to drive than heretofore, which is relatively quiet during the operation thereof, and which can be reversed about its longitudinal axis to provide new sharp cutting edges without affecting the noise level thereof during its operation or increasing the power necessary to drive the same. To these ends, I provide a hammer having a cross sectionally rectangular material engaging head at its radially outer end defining sharp corner edges at the leading and trailing sides thereof, and a radially inwardly extending shank of streamline form, having uniformly curved opposite side surfaces which converge from the transversely central portion of the shank to the opposite leading and trailing side edges thereof. Specifically, the hammer of this invention comprises a shank of streamline cross section having generally rectangular heads at the opposite ends thereof, enabling the hammer to be reversed end for end as well as about its longitudinal axis, to provide a maximum quantity of cutting edges available for use.

Brief description of the drawings Referring to the drawings, which illustrate the invention, and in which like reference characters indicate like parts throughout the several views:

3,357,584 Patented F oh. 6, 1968 FIG. 3 is a transverse section taken on the line 33 of FIG. 2.

Description of the preferred embodiment Referring with greater detail to the drawings, the numeral 1 indicates, in its entirety, a supporting structure including legs 2, two of which are shown. The frame structure 1 further includes a pair of spaced vertical walls 3, one of which is shown, which walls 3 comprise the end walls of a hopper 4 having downwardly converging side wall portions 5 and an arcuate bottom wall portion 6. A conventional screw conveyor 7 is disposed in the bottom portion of the hopper 4 for delivery of ground material therefrom.

The vertical walls 3 further provide end walls of a generally cylindrical housing 7 having a semi-cylindrical perforated wall or screen 8 and a cross-sectionally arcuate closure member 9 that is hingedly mounted, as at 10, to a top wall 11 of an infeed chute 12. The closure 9 is normally held in a closed position by a conventional hasp or locking device 13, and cooperates with the perforate wall 8 and walls 3 to define a mill chamber 14. Material to be ground is introduced to the mill chamber 14 through the infeed chute 12 by suitable means, such as a vaned feeding wheel 15 and a conventional screw conveyor 16, the wheel 15 and conveyor 16 being both used when it is desired to introduce different materials simultaneously to the mill chamber 14, to be ground together.

A grinding rotor 17 comprises a central shaft 18 that extends axially of the mill chamber 14, a plurality of disclike mounting members 19, one of which is shown keyed or otherwise mounted on the shaft 18 for common rotation therewith, and a plurality of circumferentially and axially spaced hammers 20 that are journalled on circumferentia-lly spaced mounting rods or studs 21 which extend through the mounting plates 19. The shaft 18 may be assumed to be journalled in suitable bearings, not shown, and driven at various desired speeds from a suitable source of power through conventional means including a drive shaft 22, a change gear mechanism 23 and other power transmission mechanism, not shown.

With the exception of the particular structure of the hammers 20, hammer mills of the type above described are well known; and, inasmuch as the mill in and of itself does not comprise the instant invention, further detailed showing and description thereof is omitted, in the interest of brevity. It should suffice to state that, the hammers 20 are usually journalled on their respective mounting rods 21 and, when the rotor 17 is stationary, the hammers 20 depend generally downwardly from their respective rods 21. During rotation of the rotor 17, the hammers 20 assume radially outwardly projecting positions as illustrated in FIG. 1.

'One of the rotors 20 of this invention is shown in detail in FIGS. 2 and 3, and comprises an elongated blade-like shank 24 and a pair of rectangular working heads 25 each disposed at an opposite end of the shank 24 and integrally formed therewith. Each head 25 has opposed side surfaces 26, opposed edge surfaces 27 and outer end surfaces 28, the side surfaces 26 cooperating with the edge surfaces 27 to provide sharp corner edges 29 extending longitudinally of the hammer 20. The outer end surfaces 28 cooperate with their adjacent edge surfaces 27 to define sharp corner edges 30 extending generally transversely of the hammer 20 and of the direction of rotation of the hammer 20 when the same is rotatively mounted in a hammer mill.

Intermediate the heads 25, the shank 24 is formed to provide curved opposite side surfaces 31 which converge from the transversely central portion of the shank 24 to the opposite side edges thereof, see particularly FIG. 3. Th shank 24 is equal in width to the heads 25, the shank 24 at its transversely central portion being substantially equal in thickness to the thickness of the heads 25. As shown, the converging side surfaces terminate at side edge portions 32 that are disposed in the planes of their adjacent edge surfaces 27 of the heads 25, the edge portions 32 being of substantially less thickness than the heads 25. The curvature of the sides 31 and narrow transverse dimensions of the edge portions 32 providing a shank that is highly streamlined. The shank 24 is further bored to provide a pair of longitudinally spaced transverse mounting apertures 33 each adjacent a different one of the heads 25 for selective reception of a mounting rod or stud 21. It will be further noted that the edge portions 32 of the shank 24 define relatively sharp corner edges 34, adjacent ones of which are disposed in closely spaced parallel relationship.

As rotation is imparted to the rotor 17, one of the edge portions 32 of each hammer 20 becomes a leading edge, the opposite edge portion 32 being the trailing edge of each hammer 20. As material is fed to the mill chamber 14, the radially outer portion of each leading edge 32 and the adjacent edge surface 27 of each radially outwardly disposed head 25 continges on the material, the impact thereof breaking the material particles into smaller sizes. Further, the leading corner edges 29 and 30 of the radially outer heads 25, together with the leading corner edge portions 34 adjacent thereto, have a cutting effect on the material to further reduce the size of the particles thereof. Continued use of the mill causes these leading corner edges to be worn to a rounded condition. When this occurs, the hammers 20 may be disassembled from their respective mounting plates 19 and rotated on their longitudinal axes so that the former leading edges of the hammers become the trailing edges thereof, and the hammers remounted on their respective mounting plates 19. After both side edges of the outer end portions of the hammers are dulled, the hammers 20 may again be dismounted from their mounting plates 19 and each turned end for end and remounted so that a new set of sharp corner edges 29, 30 and 34 are presented to the material to be ground. When these become worn, the hammers 20 may be again rotated on their longitudinal axes as above described. Thus, each hammer 20 has a total of four material-engaging portions which may be used selectively as wear occurs.

The curvature of the sides 31 of each shank 24 is substantially the same at either side of the longitudinal axis f the hammer 20 toward either edge portion 32 thereof making for a highly efficient streamline form when either side edge portion 32 is the leading or trailing edge of the hammer. This streamline form of the shank portions 24 of the hammers 20 reduces to a considerable degree the turbulence that is normally found in hammer mills having hammers of the usual variety made from cross-sectionally rectangular bar stock. This reduction in turbulence has been found to materially reduce the noise level within the mill chamber 14, as well as the power required to rotate the rotor 17 in normal operation of the mill. Further, the decreased turbulence has been found to eliminate the necessity for use of a fan and dust collector for removal of dust which otherwise occurs in hammer mills,

While I have shown and described a commercial embodiment of my hammer mill hammer, it will be understood that the same is capable of modification without departure from the spirit and scope of the invention, as defined in the claims.

What I claim is:

1. A hammer for hammer mills comprising, an elongated blade-like shank and a head at one end of aid shank, said head being cross sectionally rectangular and defining sharp corner edges, said shank including means for mounting said hammer to a rotary member of a hammer mill for common rotation with said rotary member, said shank having uniformly curved opposite side surface portions which converge from the transversely central portion of the shank to the opposite side edges thereof.

2. The hammer mill defined in claim 1, in which said head has a predetermined width and thickness, said shank having a thickness at its transversely central portion substantially equal to the thickness of said head.

3. The hammer mill defined in claim 1, in which said side edges and said curved side surface portions of the shank cooperate to define sharp corner edges adjacent said head.

4. The hammer mill defined in claim 1, in which said shank and head are integrally formed from a single piece of stock.

5. The hammer defined in claim 1 in which the width of said shank is substantially equal to the width of said head.

6. A hammer for hammer mills comprising, an elongated blade-like shank formed at its opposite ends to provide a pair of rectangular heads having sharp corner edges, the opposite end portions of said shank adjacent said heads having transverse apertures therethrough for selectively receiving a rotary portion of a hammer mill, whereby to mount said hammer for common rotation with said rotary portion, said shank having curved opposite side surfaces which converge from the transversely central portion of the shank to the opposite side edges thereof to provide a cross section of streamline form between said heads.

7. The hammer defined in claim 6 in which said heads have a predetermined uniform width and thickness, said shank having a width substantially equal to the width of said heads, the thickness of said shank at the transversely central portion thereof being substantially equal to the thickness of said heads.

References Cited UNITED STATES PATENTS 1,954,175 4/1934 Jensen 241- 2,424,316 7/1947 Johnson 241197 2,477,628 8/1949 Lanter 241-192 2,607,538 8/1952 Larson 241-172 3,131,875 5/1964 Szegvari 241-472 3,254,687 6/1966 Tertyshinkov 241191 FOREIGN PATENTS 28,388 12/1903 Great Britain. 703,371 3/1941 Germany WILLIAM W. DYER, JR., Primary Examiner.

R. J. ZLOTNIK, Assistant Examiner. 

